Electric circuit breaker



May .23, 1939 L. s. HoBsoN 2,159,829

ELECTRIC CIRCUIT BREAKER Filed May lO, 1934 2 Sheets-Sheet l IDVGTYCO r Leland S. Hobsom May 23, 1939- L. s, HoBsoN 2,159,829

ELECTRIC CIRCUI T BREAKER Filed May 1o, 1934 2 sheets-sheet 2 I rwentor Le I and S. Hobson` His Attici-neg.

* atented May 23, 1939 UNITED STATES York Claims.

My invention relates to electric circuit breakrs of the fluid-break type wherein relatively mov- Ible contact structure is immersed in arc-extinw-uishing or insulating liquid, vas cil, and has for ts principal object the provision of an improved circuit breaker of the aforesaid type which shall have appreciably increased interrupting capacity and be efficient in operation and simple, compact and rugged in construction.

Oil circuit breakers of the well known plainbreak type wherein a contact bridging member is lowered within an oil-containing switch casing or tank to interrupt the circuit are more or less fortuitous in operation and cannot with any degree ofV certainty be relied upon consistent- 1y 'to-interrupt large power currents under similar load conditions. This is due to the fact that the generation of gas by action of the arc on the oil results in conducting gas bubbles of appreciable volume at the breaks or points ofv contact separation tending to support arcing unless broken up sufficiently by oil turbulence in the switch. The switch casing, which is but partially filled with oil, does not have a confining or restraining eiect on the body of oil through which the bridging member descends with the result that the sudden generation of pressure upon opening of the circuit throws a large volume of oil upwardly into the air space of the switch casing. The region adjacent the separating contacts is, therefore, but partly filled with oil at the time when an insulating liquidv is most needed.

The. bridging member may, therefore, be lowered varying distances in opening the circuit under similar load conditions before the insulating medium between the contacts has sufficient dielectric strength to interrupt the circuit at a current zero. Furthermore, if the circuit is not cleared when the bridging member reaches its D lower limit of travel, failure of the breaker and adangerous explosion and oil fire may result;

In accordance with my invention, the interrupting capacity of the circuit breaker is increased and greater reliability is obtained by baille structure having a confining effect on the body of insulating liquid into which the movable contact structure is projected upon opening of the circuit, said barile however being arranged so as to direct away from the contact structure the immediate ,0 escape of gas forr'ned at each of the breaks.

My application, Serial No. 240,782, led November 16, 1938, for Electric circuit breakers, is a division of the present application.

Referring more particularly to the drawings, .5 Fig. 1 is an elevational view, partly in section,

PATENT OFFICE ELEc'rmc cracorr :mamma Leland S. Hobson, Yeadon, Pa., assigner to General Electric Company, a corporation of New Application May 1o, 1994, serial No. 724,864

' (ci. zoo-15o) of an oil circuit breaker embodying my invention; Fig. 2 is a plan sectional view taken along the line 2 2 of Fig. 1, and Figs. 3, 4, 5 and 6 are elevational views, partly in section, of modified forms of my invention.

The oil circuit breaker illustrated by Figs. 1 and 2 comprises a switch casing I formed by an oil-containing tank 2 and a cover member or dome 3, and relatively movable contact structure 4 disposed within the casing and immersed in the oil or insulating liquid 5. The contact structure may be of the well known blade-and-flnger type, the stationary contacts 6 and 1 comprising spring mounted nger contact members arranged to be spread apart and interconnected, as illustrated, by the conducting bridging member 8. The stationary contacts S and I are connected to and supported at the lower ends of the lead-in conductors 9 and I0 which extend into the switch casing through the cover 3. The lead-in conductors 9 and I0 are supported by insulating bushings I I and I2, respectively, and are suitably mechanically and electrically connected to the stationary contacts as by clamping means I3 and I4, respectively.

Opening and closing of the circuit are effected by reciprocal vertical movement of the bridging member 8 which is connected to a lift-rod I5 in turn operatively connected to suitable actuating means (not shown) as at I6. The oil circuit breaker structure so far described is conventional and opening of the circuit is effected simply by lowering the bridging member 8 within the oil body so that two breaks in series are formed between opposite ends of the bridging member and the arcing contact fingers 6' and l.

For the purpose of producing a restraining or confining effect on the oil body between the stationary contacts 6 and "I, into which the bridging member 8 is projected during the circuit opening operation, insulating baiile structure arranged in addition to provide immediate and direct escape of gas formed at both of the contact breaks is employed. In the present instance (Figs. 1 and 2) I have illustrated a plate-like insulating baille I1 horizontally disposed'beneath the surface of the oil 5. and immediately above the stationary contacts 6 and l. The insulating baiiie I'I is suitably composed of an impregnated laminated structure which is mechanically strong and of good insulating characteristics. With the exception of apertures I8 and I9 through which the lead-in conductor structure and lift rod I5 extend respectively, the baie I1 is continuous between the stationary contacts and, as illustrated HES Till

by Fig. 2, fits closely against the side walls of the switch tank 2. By way of example, but without limitation thereto, a polyphase circuit breakerl is illustrated, the contact structure of the individual phases being similar and arranged to operate simultaneously.

The baffle il is provided with apertures or cutaway portions 2t and 2i at opposite sides thereof immediately adjacent and opposite the breaks oi each individual phase. As clearly illustrated by Fig. 2, semicircular portions may be conveniently cut away from the' opposite edges of the bafile so as to afford direct and immediate escape oi gas formed at the contact breaks, and the continuous portion of the baffle prevents the main body of oil around the contact structure from being thrown into the air space of the switch casing. Accordingly, the bridging member is lowered through a substantially uniform oil body instead of through a mixture of oil and gas as in the operation of the conventional plain-break oil circuit breaker.

The immediate escape of gas from the breaks at the opposite sides of the switch casing upwardly through the apertures 2u and 2l into the air space without appreciably disturbing the main oil body, therefore, not only eliminates a factor tending to cause prolonged arcing but also insures comparatively rapid interruption of the circuit by reason of the uniform oil body about the bridging memloer when the arc current passes through zero.

Fig. 3 illustrates a modified form of my invention which may be used where large short circuit currents may be encountered. Since the pressure developed within the switch casing by arcing depends on the magnitude of the arc current, it willdbe apparent that very large pressures may su enly be generated within the switch casing when the switch is opened on a short circuit. In Fig. 3 the insulating baffle 22 is slidably guided on the insulating bushings Il and l2 and is spring-biased, as by compression springs 23, so as to oppose arc pressure generated beneath the same at the contact breaks. A stationary abutment 24 for springs 23 is suitably secured to the bushings H and I2.

As in the previous instance, the insulating baffle 22 tends to confine the oil body beneath the same and between the contacts 6 and 1 and to dlrect immediate escape of gas at the contact breaks upwardly through the side apertures 25 and 26. The springs 23 normally o-ppose moderate pressures within the tank but yield upon the occurrence of high pressures so as to relieve, to a certain extent, the bursting pressure within the switch casing. YImmediately upon decrease of pressure the baille 22 returns to its normal position as illustrated.

The resiliently mounted baille 22 likewise serves to increase the efliciency and interrupting capacity of the circuit breaker. When gas bubbles form at the breaks upon initial separation of the contacts, the volume thereof obviously depends upon the pressure exerted on the same by the oil body and bythe magnitude of the arc current. When the current is at the maximum value of thedcycle, gas is being generated at a maximum rate, the converse being true when the current reaches the zero point of the cycle. Accordingly, upon formation of the gas bubble due to maximum current, the baffle 22 is biased upwardly, thereby relieving the switch tank oi excessive pressures and storing energy in the springs the gas bubble meanwhile escaping upwardly along the side walls of the swltci'i tari;

at opposite sides of the bams. When the current however, i'alls to zero the pressure within `th switch casing decreases so that the baffle 22 utilizing the stored energy in the springs 23 serves to place the oil beneath the same under pressure and thereby to reduce the size of the gas bubble existing between the contacts. Accordingly, at the current zero the gas bubble is of minimum volume and consequently more oil is available at the separating contacts at a time when it is most eflectivo.

Fig. 4 illustrates an arrangement wherein an air or gas cushion is used in lieu of a spring biased baille plate generally for the purpose above described. In this case the insulating baille 21 is suitably positioned a short distance above the oil level so 'that an air space 2l oi the desired proportions is provided. in order to restrain vthe oil through which the bridge 8 is lowered, the baille 2l is provided with depending ilanges 28 and 2Q which extend across the switch tank 2 so as to form with the sides thereof chimney-like passages 23 and 29 for the direct and immediate escape of gas from the breaks at fi and l'. The air cushion at 2l. is comned beneath the baille structure and is so proportioned with respect to the interrupting capa-city and operating requirements of the breaker that no oil-throw 'takes place. The energy stored in the air cushion during circuit interruption is effective, as in the previous instance, to aid interruption of arcing at a current zero and to force out gas through the passages 28 and 29.

It will be apparent that the feature of my invention relating to decrease of the volume of the gas bubble at the current zero while affording means for causing the immediate and direct escape thereof, without disturbing the oil body into which the bridging contact is projected, is not limited to the specific arrangements illustrated by Figs. 3 and 4. For example, the baille may be rigidly mounted as in Figs. 1 and 2 and the side walls of the switch casing 2 made suf- ;ficiently flexible so that not only are the peak pressures reduced but the gas bubble is compressed to 'comparatively small volume at the current zere due to return of the energy stored in the ilexible switch walls during the high current values.

Fig. 5 illustrates another form of my invention wherein the insulating baffle 2'1 is immersed in the oil and provided as in Fig. 4 with depending anges or side walls 28 and 29 extending adjacent the tips of the arcing contacts 6. The flanges 28 and 29 are spaced, as illustrated, a. suitable distance with respect to the side walls of the casing 2 so as to form chimney-like passages 28 and 29 for immediate and direct escape of the gas bubble. It will be apparent that the crs sectional area of the passages 28' and 25 may be varied to suit the operating requirements of the breaker. The present arrangement has the effect of bringing the baille 21 to a level adjacent the tips of the arcing contacts so that direct gas exhaust is effected and a minimum amount of gas is present around the stationary contact structure upon opening of the circuit.

As previously described, the elimination and decrease in volume of the gas adjacent the separating contacts is highly desirable in order to increase the effectiveness of the insulating oil. In the present arrangement the oil body intermediate the lower tips oi the stationary contact is not subject to displacement by the gas pressure and the gas itself under pressure tends to exr pand directly into the passagean' and 29 as in Fig. 4.

In the arrangement shown in Fig. 6 the insulating baiie structure 30 comprises wall structure 3| and 32 depending from an insulating plate portion 33 and having apertures 34 and 35 immediately adjacent and .opposite the breaks formed upon initial separation of the contacts. This arrangement is generally similar in principle to that shown in Fig. 5 except that the partially enclosing wall structure has a more confining effect on the lower portion of the oil body. Upon initial separation of the contacts the gas bubbles under pressure immediately escape through the openings 34 and 35 and the oil beneath the bridging contact 8 is confined so that there is comparatively little turbulence therein. 'I'he bridging member 8 therefore descends through insulating oil, instead of a mix.-

ure of gas and oil with the result that the circuit is more effectively interrupted and the interrupting capacity of the breaker increased.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modiilcations may occur to one skilled in the art Without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. An electric circuit breaker of the iluid-break type comprising a casing containing an insulating liquid, relatively movable contact structure immersed in said liquid including a pair-of stationary contacts and a movable bridging member, an insulating baille comprising a substantially ilat plate disposed beneath the surface of said liquid and immediately above said stationary contacts, said baille being horizontally positioned and engaging the side Walls of said casing so as to form upper and lower chambers therein, said baille being substantially continuous between said side walls except for apertures formed therein at opposite edges of said baille so that a separate aperture is opposite each of said stationary contacts.

2. An electric circuit breaker of the fluid-break type comprising a casing containing an insulating liquid, relatively movable contact structure forming two breaks in series immersed in said liquid, baffle structure disposed beneath the surface of said liquid immediately above said contact structure, said baille having a coniining effect on the body of liquid beneath the same between said breaks and arranged to form pressure relief passages opposite said breaks adjacent the side walls of said casing for directing immediate and direct escape of gas generated by arcing, and means resiliently biasing said baille in opposition to arc pressure in said casing, said pressure relici.| passages being completely open in all positions of said baille.

3. An electric circuit breaker of the fluid-break type comprising a casing containing an arc-extinguishing liquid,v relatively movable contact structure immersed in said liquid including a pair of stationary contacts and a movable bridging member, an insulating plate-like member forming a baie beneath the surface of said liquid and positioned horizontally closely above said stationary contacts, said bale at opposite edges engaging side walls of said casing so as to form upper and lower chambers therein, said baille being substantially continuous between said side walls except for a plurality of notch-like apertures formed at said edges so that a separate aperture communicating with the upper chamber is closely adjacent to and above each of said stationary contacts.

4. An electric circuit breaker of the iluid-break type comprising a casing containing an arc-extinguishing liquid, relatively movable contact structure including a pair of stationary insulating lead-in conductor studs, xed arcing contacts immersed in said liquid secured to said studs `at the lower ends thereof and a movable bridging member coacting with said arcing contacts, and an insulating baille comprising a substantially flat plate horizontally disposed beneath the surface of said liquid substantially at the lower ends of said insulating studs and in juxtaposition to said arcing contacts, said baille cooperating with side walls of said casing so as to form upper and lower chambers therein, said baille being substantially continuous between said side walls except for apertures formed between the opposite edges of said baille and said casing so that an exhaust aperture is located immediately opposite and above each ot said stationary contacts.

5. An electric circuit breaker of the fluid-break type comprising a casing containing an arc-extinguishing liquid, relatively movable contact structure arranged to form two breaks in series immersed in said liquid, a pair oi.' insulating leadin conductor studs extending into said casing and connected to said contact structure, insulating plate-like baille structure positioned horizontally above and in juxtaposition to said contact structure, said baille having a conilning eifect on the body of liquid between said breaks and arranged to form pressure reliei.l passages opposite said breaks adjacent opposite side walls of said casing, said baille being guided for limited reciprocal vertical movement at the lower ends of said studs, and spring means for biasing said baille in opposition to arc pressure generated beneath the same at said breaks.

LELAND S. HOBSON. 

